This invention relates to a fiber cutting machine, and more particularly to a machine for cutting a fibrous tow, usually a tow of synthetic plastic filaments into staple fibers, i.e., for severing it into sections of reduced length.
A machine of this type is already known from German Published Application OS No. 2,809,592 which uses a rotary cylinder from which cutter blades project in radial direction. A stationary tow guiding ring coaxially surrounds the cylinder and the tow is guided between the ring and the cylinder to form convolutions which are cut-through by the blades. This machine has many advantageous aspects, such as its structural simplicity, exact operation and low blade wear. It does, however, have the problem that sliding friction develops between the stationary ring and the tow convolutions which participate in the rotation of the cylinder. At the high operating speeds which are now required of these machines to make their use economically feasible, this sliding friction tends to cause heating of the materials involved and may lead to consequent damage to these materials. This is aggravated by the fact that the advancement of the convolutions on the cylinder generates additional friction.
Another machine for the same purpose is described in British Pat. No. 1,424,178. It uses a circular plate carrying an annulus of axially parallel blades having outwardly facing cutting edges. The tow guiding ring surrounds the plate with its own axis parallel but eccentric relative to the axis of the plate so that at one side its inner surface is very close to the cutting edges whereas at the opposite side there is a sickle-shaped clearance between them. In this machine the ring is turnably mounted so that the sliding-friction problem mentioned above is avoided. However, the area of contact between the ring and the tow convolutions is relatively small, which results in a somewhat uneven operation and rather high blade wear.